Haptophytes | |
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Coccolithophore ( Coccolithus pelagicus ) | |
Scientific classification | |
Domain: | Eukaryota |
Clade: | Diaphoretickes |
Phylum: | Haptista |
Subphylum: | Haptophytina Hibberd, 1976 stat. nov. Cavalier-Smith, 2015 [1] |
Classes & orders | |
Synonyms | |
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The haptophytes, classified either as the Haptophyta, Haptophytina or Prymnesiophyta (named for Prymnesium ), are a clade of algae.
The names Haptophyceae or Prymnesiophyceae are sometimes used instead. [2] [3] [4] This ending implies classification at the class rank rather than as a division. Although the phylogenetics of this group has become much better understood in recent years, there remains some dispute over which rank is most appropriate.
The chloroplasts are pigmented similarly to those of the heterokonts, [5] but the structure of the rest of the cell is different, so it may be that they are a separate line whose chloroplasts are derived from similar red algal endosymbionts.
The cells typically have two slightly unequal flagella, both of which are smooth, and a unique organelle called a haptonema , which is superficially similar to a flagellum but differs in the arrangement of microtubules and in its use. The name comes from the Greek hapsis, touch, and nema, round thread. The mitochondria have tubular cristae.
The best-known haptophytes are coccolithophores, which make up 673 of the 762 described haptophyte species, [6] and have an exoskeleton of calcareous plates called coccoliths. Coccolithophores are some of the most abundant marine phytoplankton, especially in the open ocean, and are extremely abundant as microfossils, forming chalk deposits. Other planktonic haptophytes of note include Chrysochromulina and Prymnesium , which periodically form toxic marine algal blooms, and Phaeocystis , blooms of which can produce unpleasant foam which often accumulates on beaches. [7]
Haptophytes are economically important, as species such as Pavlova lutheri and Isochrysis sp. are widely used in the aquaculture industry to feed oyster and shrimp larvae. They contain a large amount of polyunsaturated fatty acids such as docosahexaenoic acid (DHA), stearidonic acid and alpha-linolenic acid. [8] Tisochrysis lutea contains betain lipids and phospholipids. [9]
The haptophytes were first placed in the class Chrysophyceae (golden algae), but ultrastructural data have provided evidence to classify them separately. [10] Both molecular and morphological evidence supports their division into five orders; coccolithophores make up the Isochrysidales and Coccolithales. Very small (2-3μm) uncultured pico-prymnesiophytes are ecologically important. [7]
Haptophytes was discussed to be closely related to cryptomonads. [11]
Haptophytes are closely related to the SAR clade. [12]
Subphylum Haptophytina Cavalier-Smith 2015 [Haptophyta Hibberd 1976 sensu Ruggerio et al. 2015] [13]
The Stramenopiles, also called Heterokonts, are a clade of organisms distinguished by the presence of stiff tripartite external hairs. In most species, the hairs are attached to flagella, in some they are attached to other areas of the cellular surface, and in some they have been secondarily lost. Stramenopiles represent one of the three major clades in the SAR supergroup, along with Alveolata and Rhizaria.
The centrohelids or centroheliozoa are a large group of heliozoan protists. They include both mobile and sessile forms, found in freshwater and marine environments, especially at some depth.
Pedinellales (ICN) or Pedinellida (ICZN) is a group of single-celled algae found in both marine environments and freshwater.
Chromista is a proposed but polyphyletic biological kingdom, refined from the Chromalveolata, consisting of single-celled and multicellular eukaryotic species that share similar features in their photosynthetic organelles (plastids). It includes all eukaryotes whose plastids contain chlorophyll c and are surrounded by four membranes. If the ancestor already possessed chloroplasts derived by endosymbiosis from red algae, all non-photosynthetic Chromista have secondarily lost the ability to photosynthesise. Its members might have arisen independently as separate evolutionary groups from the last eukaryotic common ancestor.
The Chrysophyceae, usually called chrysophytes, chrysomonads, golden-brown algae or golden algae, are a large group of algae, found mostly in freshwater. Golden algae is also commonly used to refer to a single species, Prymnesium parvum, which causes fish kills.
Streptophyta, informally the streptophytes, is a clade of plants. The composition of the clade varies considerably between authors, but the definition employed here includes land plants and all green algae except the Chlorophyta and the more basal Prasinodermophyta.
Ochrophytes, also known as heterokontophytes or stramenochromes, are a group of algae. They are the photosynthetic stramenopiles, a group of eukaryotes, organisms with a cell nucleus, characterized by the presence of two unequal flagella, one of which has tripartite hairs called mastigonemes. In particular, they are characterized by photosynthetic organelles or plastids enclosed by four membranes, with membrane-bound compartments called thylakoids organized in piles of three, chlorophyll a and c as their photosynthetic pigments, and additional pigments such as β-carotene and xanthophylls. Ochrophytes are one of the most diverse lineages of eukaryotes, containing ecologically important algae such as brown algae and diatoms. They are classified either as phylum Ochrophyta or Heterokontophyta, or as subphylum Ochrophytina within phylum Gyrista. Their plastids are of red algal origin.
Phaeothamniophycidae is a subclass of heterokont algae. It contains two orders, Phaeothamniales and Pleurochloridellales, and consists of species separated from Chrysophyceae.
Opalozoa is a subphylum of heterotrophic protists of the phylum Bigyra, and is the sister group to Sagenista. Opalozoans are non-photosynthetic heterokonts that are ancestrally phagotrophic but many times have evolved to be osmotrophic saprotrophs in the gut of vertebrate animals.
Dictyochophyceae sensu lato is a photosynthetic lineage of heterokont algae.
The cryptomonads-haptophytes assemblage is a proposed but disputed monophyletic grouping of unicellular eukaryotes that are not included in the SAR supergroup. Several alternative names have been used for the group, including Hacrobia ; CCTH ; and "Eukaryomonadae".
Prymnesium is a genus of haptophytes, including the species Prymnesium parvum. The genus is a unicellular motile alga. It is ellipsoidal in shape one flagellum is straight and there are two longer ones which enable movement.
Chrysochromulina is a genus of haptophytes. This phytoplankton is distributed globally in brackish and marine waters across approximately 60 known species. All Chrysochromulina species are phototrophic, however some have been shown to be mixotrophic, including exhibiting phagotrophy under certain environmental conditions. The cells are small, characterized by having scales, and typically observed using electron microscopy. Some species, under certain environmental conditions have been shown to produce toxic compounds that are harmful to larger marine life including fish.
A protist is any eukaryotic organism that is not an animal, plant, or fungus. The protists do not form a natural group, or clade, since they exclude certain eukaryotes with whom they share a common ancestor; but, like algae or invertebrates, the grouping is used for convenience. In some systems of biological classification, such as the popular five-kingdom scheme proposed by Robert Whittaker in 1969, the protists make up a kingdom called Protista, composed of "organisms which are unicellular or unicellular-colonial and which form no tissues". In the 21st century, the classification shifted toward a two-kingdom system of protists: Chromista and Protozoa.
Haptista is a proposed group of protists made up of centrohelids and haptophytes. Phylogenomic studies indicate that Haptista, together with Ancoracysta twista, forms a sister clade to the SAR+Telonemia supergroup, but it may also be sister to the Cryptista (+Archaeplastida). It is thus one of the earliest diverging Diaphoretickes.
Picophagea, also known as Synchromophyceae, is a class of photosynthetic stramenopiles. The chloroplast of the Synchromophyceae are surrounded by two membranes and arranged in a way where they share the outer pair of membranes. The entire chloroplast complex is surrounded by an additional two outer membranes.
Chrysochromulina ericina virus 01B, or simply Chrysochromulina ericina virus (CeV) is a giant virus in the family Mimiviridae infecting Haptolina ericina, a marine microalgae member of the Haptophyta. CeV is a dsDNA virus.
Rappephyceae, or Rappemonads, are a small family of protists first described in 2011, of uncertain phylogenic affinity. It has been discussed as a possible member of a larger clade Haptophyta. This newly identified taxonomic class of phytoplankton are named after a professor from the Hawai’i institute of marine biology, known as Michael Rappé. Rappé discovered these phytoplankton in the Atlantic Ocean and published his findings on their DNA in 1998. Current research has shown that these organisms provide an immense amount of nutritional organic molecules, such as oxygen, for other organisms using biochemical processes like photosynthesis and carbon fixation.
Gyrista is a phylum of heterokont protists containing three diverse groups: the mostly photosynthetic Ochrophyta, the parasitic Pseudofungi, and the recently described group of nanoflagellates known as Bigyromonada. Members of this phylum are characterized by the presence of a helix or a double helix/ring system in the ciliary transition region.
Rebecca is a genus of photosynthetic, flagellated marine haptophytes. It is one of four genera in the family Pavlovaceae. The holotype species, R. salina, was described in 2000 by J.C. Green; it is one of three species currently accepted in the genus. Also in the genus is R. helicata, which was described in the same publication as R. salina, and the third member is R. billiardiae, which was described in 2023. R. helicata and R. salina were both previously considered to be within the genus Pavlova.